#ifndef GBAEXP_COMMON_H
#define GBAEXP_COMMON_H

#include "shorthand.h"

//
// Memory sections.
//

// Defines for the different memory sections in the GBA.
#define MEM_SROM  0x00000000
#define MEM_EW    0x02000000
#define MEM_IW    0x03000000
#define MEM_IO    0x04000000
#define MEM_PAL   0x05000000
#define MEM_VRAM  0x06000000
#define MEM_OAM   0x07000000
#define MEM_PAK   0x08000000
#define MEM_CART  0x0E000000

//
// Display modes.
//

// Display registers.
#define DISP_CTRL   *((vu32*)(MEM_IO + 0x0000))
#define DISP_STATUS *((vu16*)(MEM_IO + 0x0004))
#define DISP_VCOUNT *((vu16*)(MEM_IO + 0x0006))

// The first three bits in the DISP_CTRL are used to control the video mode.
#define DISP_MODE_0     0x0000
#define DISP_MODE_1     0x0001
#define DISP_MODE_2     0x0002
#define DISP_MODE_3     0x0003
#define DISP_MODE_4     0x0004
#define DISP_MODE_5     0x0005
#define DISP_GB         (1 << 3)
#define DISP_PAGE       (1 << 4)
#define DISP_OAM_HBLANK (1 << 5)
#define DISP_OBJ_1D     (1 << 6)
#define DISP_BLANK      (1 << 7)
#define DISP_BG_0       (1 << 8)
#define DISP_BG_1       (1 << 9)
#define DISP_BG_2       (1 << 10)
#define DISP_BG_3       (1 << 11)
#define DISP_OBJ        (1 << 12)
#define DISP_ENABLE_SPRITES DISP_OBJ | DISP_OBJ_1D

// Registers to control of BG layers.
#define BG_CTRL_0 *((vu16*)(0x04000008 + 0x0002 * 0))
#define BG_CTRL_1 *((vu16*)(0x04000008 + 0x0002 * 1))
#define BG_CTRL_2 *((vu16*)(0x04000008 + 0x0002 * 2))
#define BG_CTRL_3 *((vu16*)(0x04000008 + 0x0002 * 3))

// Bits to control the background.
#define BG_PRIORITY_0     0x0
#define BG_PRIORITY_1     0x1
#define BG_PRIORITY_2     0x2
#define BG_PRIORITY_3     0x3
#define BG_CHARBLOCK(N)   ((N) << 2)
#define BG_MOSAIC         (1 << 6)
#define BG_HIGH_COLOR     (1 << 7)
#define BG_SCREENBLOCK(N) ((N) << 8)
#define BG_AFFINE         (1 << 0xD)
#define BG_SIZE(N)        ((N) << 0xE)

// BG registers for horizontal displacement.
#define BG_H_SCROLL_0 *((vu16*)(0x04000010 + 0x0004 * 0))
#define BG_H_SCROLL_1 *((vu16*)(0x04000010 + 0x0004 * 1))
#define BG_H_SCROLL_2 *((vu16*)(0x04000010 + 0x0004 * 2))
#define BG_H_SCROLL_3 *((vu16*)(0x04000010 + 0x0004 * 3))

// BG registers for vertical displacement.
#define BG_V_SCROLL_0 *((vu16*)(0x04000012 + 0x0004 * 0))
#define BG_V_SCROLL_1 *((vu16*)(0x04000012 + 0x0004 * 1))
#define BG_V_SCROLL_2 *((vu16*)(0x04000012 + 0x0004 * 2))
#define BG_V_SCROLL_3 *((vu16*)(0x04000012 + 0x0004 * 3))

// Screenblocks for BGs.
typedef u16 ScreenBlock[1024];
#define SCREENBLOCK_MEM ((ScreenBlock*)MEM_VRAM)

// Screenblock entry bits.
#define SCREENBLOCK_ENTRY_H_FLIP (1 << 0xA)
#define SCREENBLOCK_ENTRY_V_FLIP (1 << 0xB)
#define SCREENBLOCK_ENTRY_PAL(N) ((N) << 0xC)

size_t se_index(size_t tile_x, size_t tile_y, size_t map_width) {
    size_t sbb = ((tile_x >> 5) + (tile_y >> 5) * (map_width >> 5));
    return sbb * 1024 + ((tile_x & 31) + (tile_y & 31) * 32);
}

// Screen settings.
#define SCREEN_WIDTH 240
#define SCREEN_HEIGHT 160

// The GBA in mode 3 expects rbg15 colors in the VRAM, where each component
// (RGB) have a 0--31 range. For example, pure red would be rgb15(31, 0, 0).
typedef u16 Color;

// A palette is composed of 16 colors, with color at index 0 being transparent.
typedef Color Palette[16];

//
// Tile memory access.
//

// NOTE: Only defining 4bpp tiles for now.
typedef struct Tile {
    u32 data[8];
} Tile;

typedef Tile TileBlock[512];
#define TILE_MEM ((TileBlock*) MEM_VRAM)

// We can treat the screen as a HxW matrix. With the following macro we can
// write a pixel to the screen at the (x, y) position using:
//
//     FRAMEBUFFER[y][x] = color;
//
typedef Color Scanline[SCREEN_WIDTH];
#define FRAMEBUFFER        ((Scanline*)MEM_VRAM)
#define SCREEN_BUFFER      ((u16*) MEM_VRAM)
#define PAL_BUFFER_BG      ((u16*) MEM_PAL)
#define PAL_BUFFER_SPRITES ((u16*) 0x05000200)
#define PAL_BANK_BG        ((Palette*) MEM_PAL)
#define PAL_BANK_SPRITES   ((Palette*) 0x05000200)

//
// Colors.
//

static inline Color
rgb15(u32 red, u32 green, u32 blue ) {
    return (blue << 10) | (green << 5) | red;
}

#define COLOR_RED   rgb15(31, 0, 12)
#define COLOR_BLUE  rgb15(2, 15, 30)
#define COLOR_CYAN  rgb15(0, 30, 30)
#define COLOR_GREY  rgb15(4, 4, 4)
#define COLOR_BLACK rgb15(0, 0, 0)
#define COLOR_WHITE rgb15(28, 28, 28)

//
// Sprites.
//

// Using macros instead of aligned structs for setting up OBJ attributes and
// affine parameters.
// TODO: Benchmark if this would be slower or the same that TONC's
// implementation.
#define OBJ_ATTR_0(N)    *((vu16*)(MEM_OAM + 0 + 8 * (N)))
#define OBJ_ATTR_1(N)    *((vu16*)(MEM_OAM + 2 + 8 * (N)))
#define OBJ_ATTR_2(N)    *((vu16*)(MEM_OAM + 4 + 8 * (N)))
#define OBJ_AFFINE_PA(N) *((vs16*)(MEM_OAM + 6 + 8 * 0 + 8 * 4 * (N)))
#define OBJ_AFFINE_PB(N) *((vs16*)(MEM_OAM + 6 + 8 * 1 + 8 * 4 * (N)))
#define OBJ_AFFINE_PC(N) *((vs16*)(MEM_OAM + 6 + 8 * 2 + 8 * 4 * (N)))
#define OBJ_AFFINE_PD(N) *((vs16*)(MEM_OAM + 6 + 8 * 3 + 8 * 4 * (N)))

// OBJ_ATTR_0 parameters
#define OBJ_Y_COORD(N)   ((N) & 0xFF)
#define OBJ_NORMAL       (0x00 << 0x8)
#define OBJ_AFFINE       (0x01 << 0x8)
#define OBJ_HIDDEN       (0x02 << 0x8)
#define OBJ_AFFINE_2X    (0x03 << 0x8)
#define OBJ_ALPHA_BLEND  (0x01 << 0xA)
#define OBJ_WINDOW       (0x02 << 0xA)
#define OBJ_SHAPE_SQUARE (0x00 << 0xE)
#define OBJ_SHAPE_WIDE   (0x01 << 0xE)
#define OBJ_SHAPE_TALL   (0x02 << 0xE)

// OBJ_ATTR_1 parameters
#define OBJ_X_COORD(N)    ((N) & 0x1FF)
#define OBJ_AFFINE_IDX(N) ((N) << 0x9)
#define OBJ_H_FLIP        (0x01 << 0xC)
#define OBJ_V_FLIP        (0x01 << 0xD)
#define OBJ_SIZE_SMALL    (0x00 << 0xE)
#define OBJ_SIZE_MID      (0x01 << 0xE)
#define OBJ_SIZE_BIG      (0x02 << 0xE)
#define OBJ_SIZE_HUGE     (0x03 << 0xE)

// OBJ_ATTR_2 parameters
#define OBJ_TILE_INDEX(N) ((N) & 0x3FF)
#define OBJ_PRIORITY(N)   ((N) << 0xA)
#define OBJ_PAL_BANK(N)   ((N) << 0xC)

static inline void
wait_vsync(void) {
    while(DISP_VCOUNT >= 160);
    while(DISP_VCOUNT < 160);
}

//
// Mode 4 page flipping
//

static inline void
flip_page(void) {
    DISP_CTRL ^= DISP_PAGE;
}

#define SCREEN_PAGE_1 ((vu16*) MEM_VRAM)
#define SCREEN_PAGE_2 ((vu16*) (MEM_VRAM + 0xa000))

//
// Profiling.
//

#define TIMER_DATA_0  *((vu16*) (0x04000100 + 0x04 * 0))
#define TIMER_DATA_1  *((vu16*) (0x04000100 + 0x04 * 1))
#define TIMER_DATA_2  *((vu16*) (0x04000100 + 0x04 * 2))
#define TIMER_DATA_3  *((vu16*) (0x04000100 + 0x04 * 3))
#define TIMER_CTRL_0  *((vu16*) (0x04000102 + 0x04 * 0))
#define TIMER_CTRL_1  *((vu16*) (0x04000102 + 0x04 * 1))
#define TIMER_CTRL_2  *((vu16*) (0x04000102 + 0x04 * 2))
#define TIMER_CTRL_3  *((vu16*) (0x04000102 + 0x04 * 3))

// Timer control bits.
#define TIMER_CTRL_FREQ_0   0
#define TIMER_CTRL_FREQ_1   1
#define TIMER_CTRL_FREQ_2   2
#define TIMER_CTRL_FREQ_3   3
#define TIMER_CTRL_CASCADE (1 << 2)
#define TIMER_CTRL_IRQ     (1 << 6)
#define TIMER_CTRL_ENABLE  (1 << 7)

// We use timers 2 and 3 to count the number of cycles since the profile_start
// functions is called. Don't use if the code we are trying to profile make use
// of these timers.
static inline
void profile_start(void) {
    TIMER_DATA_2 = 0;
    TIMER_DATA_3 = 0;
    TIMER_CTRL_2 = 0;
    TIMER_CTRL_3 = 0;
    TIMER_CTRL_3 = TIMER_CTRL_ENABLE | TIMER_CTRL_CASCADE;
    TIMER_CTRL_2 = TIMER_CTRL_ENABLE;
}

static inline
u32 profile_stop(void) {
   TIMER_CTRL_2 = 0;
   return (TIMER_DATA_3 << 16) | TIMER_DATA_2;
}

//
// Input handling.
//

// Memory address for key input register
#define KEY_INPUTS *((vu16*) 0x04000130)

// Alias for key pressing bits.
#define KEY_A      (1 << 0)
#define KEY_B      (1 << 1)
#define KEY_SELECT (1 << 2)
#define KEY_START  (1 << 3)
#define KEY_RIGHT  (1 << 4)
#define KEY_LEFT   (1 << 5)
#define KEY_UP     (1 << 6)
#define KEY_DOWN   (1 << 7)
#define KEY_R      (1 << 8)
#define KEY_L      (1 << 9)

#define KEY_MASK 0x03FF

// Saving the previous and current key states as globals for now.
static u16 key_curr = 0;
static u16 key_prev = 0;

static inline void
poll_keys(void) {
    key_prev = key_curr;
    key_curr = ~KEY_INPUTS & KEY_MASK;
}

// Returns true if the given key has been pressed at time of calling and was not
// pressed since the previous call. For example, if a key is being held, this
// function will return `true` only on the frame where the key initially
// activated.
static inline u32
key_pressed(u32 key) {
    return (key_curr & key) & ~(key_prev & key);
}

// Check if the given key is pressed and has been since at least one frame.
static inline u32
key_hold(u32 key) {
    return (key_curr & key) & key_prev & key;
}

// Check if the given key/button is currently pressed.
#define KEY_PRESSED(key) (~(KEY_INPUTS) & key)

#endif // GBAEXP_COMMON_H